Flash analog-to-digital converters (ADCs) are circuits that compare the magnitude (e.g., voltage) of an input signal against multiple threshold levels, and provide multiple output bits, with each output bit indicating a comparison result. Each output bit is generally of one binary value when the corresponding threshold level is less than the input voltage and of the other binary value otherwise. The output bits together represent a digital code corresponding to the magnitude of the input signal and can be encoded as a multi-bit binary value. Rash ADC are often used in applications that require high digitization rate, such as direct sampling radio frequency receivers.